The zoom box option uses a box to define a new viewing window. Press .

Press .
(The zoom box option can also be obtained by pressing .)

Use the cursor
keys to move the blinking cursor to locate any one of the four corners
of a box. Press .
This can serve as any one of the four corners. The cursor will change to
a box when the first corner is selected.

Move the cursor to the location of the corner of the box that is diagonal
to the first corner. As the cursor is moved, the new viewing box is visible.

When the box is the desired size, press .

Note: The window settings are adjusted and the function is graphed in the new
window.